1. Field of the Invention
This invention relates to a weather strip including a glass run and a door weather strip for an automobile.
2. Description of Related Art
A conventional glass run 50 is shown in FIGS. 6 to 8. The glass run 50 is attached to a door sash 1 of an automobile (see FIG. 5) and seals between the outer peripheral edge of a raised door window glass 2 and the door sash 1. The glass run 50 comprises a plurality of straight extruded parts 51 and curved or bent molded parts 61, each of which connects together two of the straight extruded parts 51. The extruded part 51 is attached to a straight section of the door sash 1 while the molded part 61 is attached to a corner section of the door sash 1. The letter xe2x80x9cSxe2x80x9d designates a borderline, or the connected end surfaces, between the extruded part 51 and the molded part 61.
The extruded part 51 shown in FIG. 7 comprises a channel portion 54 which consists of a bottom portion 52 and two side walls 53, and two seal lips 55 which project into the channel portion 54 from free ends of the both side walls 53 respectively. The molded part 61 shown in FIG. 8 comprises a channel portion 64 which consists of a bottom portion 62 and two side walls 63, and two seal lips 65 which project into the channel portion 64 from free ends of the both side walls 63 respectively.
Recently, attention is paid to a thermoplastic elastomer (TPE) which is superior to a rubber at the molding process. The extruded part 51 has also come to be formed from an olefin-based TPE (TPO) by extrusion molding. The molded part 61, which connects extruded parts 51 made of the TPO, is molded from a TPO or an olefin resin, either of which has high compatibility (adhesivity) to the TPO.
The end face of the outer peripheral edge of the door window glass 2 slides on the surfaces of the bottom portions 52, 62, while both side surfaces of the outer peripheral edge of the door window glass 2 slide on the surfaces of the seal lips 55, 65 respectively. Therefore, it is required to lower the frictional resistance of the surfaces of the bottom portions and seal lips to thereby enhance their slidability, and to prevent abrasion of the surfaces for improving their durability.
To meet these requirements, low-friction layers 57 made of a polyethylene resin, which have a low coefficient of friction and an excellent abrasion resistance, are formed on the surfaces of the bottom portion 52 and the seal lips 55 made of the TPO by co-extrusion simultaneously when the channel portion 54 and the seal lips 55 are formed by extrusion molding to form the extruded part 51 as a single product, as shown in FIG. 7.
As for the molded part 61 made of the TPO or the olefin resin, however, it was difficult to form the low-friction layer 57 on the surfaces of the bottom portion 62 of the channel portion 64 and the seal lips 65 when the molded part 61 was formed by injection molding as a single product, using substantially same technique of the above-described extruded part 51 forming technique, namely, simultaneously molding of the low-friction layers 57 and the channel portion 54, as shown in FIG. 8. Therefore, one could do nothing but apply liquid low-friction coating 67 made of a silicone oil or a polyurethane coating on the surfaces of the bottom portion 62 and the seal lips 65 after the molded part 61 is formed, to prevent the abrasion of the surfaces. However, the surfaces only with the liquid low-friction coating 67 were inferior to those with the above low-friction layers 57 especially in durability. Because, even if the liquid low-friction coating 67 can improve the initial slidability of the surfaces, they gradually disappear as they are used, which gradually lowers the slidability.
It is an object of this invention to provide a weather strip, which can improve the slidability and durability of the molded part.
The present invention resides in a weather strip comprising a molded part connected to an extruded part, wherein the molded part is molded from a thermoplastic elastomer or a soft resin containing a solid particle antifriction material and has 1 to 50 xcexcm of ten points average surface roughness (Rz) on the surface of the molded part. xe2x80x9cTen points average surface roughnessxe2x80x9d is a value measured in accordance with JIS B0651, JIS B0601, ISO 4287/1, ISO 4287/2, ISO4288.
Here, the molding method is not limited to a specific one. For example, cast molding, compression molding, transfer molding or injection molding can be employed.
Though xe2x80x9cTPExe2x80x9d is not limited to a specific type, it embraces an olefin-based TPE (TPO), a styrene-based TPE (SBC) and a polyester-based TPE (TPEE). The TPE having high compatibility to the extruded part is preferably used. For example, the TPO is preferably used when the extruded part is made of a TPO or an ethylene-propylene-diene copolymer (EPDM) rubber.
Though xe2x80x9csoft resinxe2x80x9d is not limited to a specific type, it embraces an olefin soft resin and a polyurethane resin (PU), a resin having high compatibility to the extruded part is preferably used. For example, an olefin soft resin is preferably used when the extruded part is made of a TPO or an EPDM rubber. The olefin soft resin embraces a soft polyethylene resin and an ethylene vinyl acetate resin (EVA).
xe2x80x9cSolid particle antifriction materialxe2x80x9d is not limited to a specific type, and it may be an antifriction material formed of solid particles of at least one material selected from the group consisting of a silicone resin, apolyamide resin, a fluorine resin, a polycarbonate resin, a mica, a molybdenum and a calcium carbonate.
The content of the solid particle antifriction material is not specifically limited, and 1 to 30% by weight for the total weight of the molding material including the antifriction material itself is preferable. Moreover, the particle size of the solid particle which forms the antifriction material is not specifically limited, and 0.1 to 50 xcexcm is preferable.
The reason why the ten points average surface roughness (Rz) on the surface of the molded part is restricted to 1 to 50 xcexcm is that the ten points average surface roughness less than 1 xcexcm lowers the effect of improving slidability of the molded part, while the ten points average surface roughness more than 50 xcexcm deteriorates the outward appearance of the molded part. 10 to 30 xcexcm of the ten points average surface roughness is more preferable. Even if the particle size of a solid particle is, for instance, 0.1 xcexcm or 1 xcexcm, the ten points average surface roughness can be, for instance, 1 xcexcm or 10 xcexcm, since a plurality of solid particles often cluster together.
The TPE or the soft resin can further contain a liquid antifriction material. The liquid antifriction material is not limited to a specific type, and it embraces a silicone oil such as polydimethylsiloxane. 0.1 to 10% by weight of the liquid antifriction material is preferably contained for the total weight of the molding material including the antifriction material itself.
The extruded part is preferably formed from a TPE or a rubber by extrusion molding, and one formed from a TPO or an EPDM rubber is more preferable.
Further objects of this invention will become evident upon an understanding of the illustrative embodiments described below. Various advantages not specifically referred to herein but within the scope of the instant invention will occur to one skilled in the art upon practice of the presently disclosed invention. The following examples and embodiments are illustrative and not seen to limit the scope of the invention.